(1) Field of the Invention
The present invention relates to a network system comprising a plurality of sub-networks, each of which connects apparatuses including a router device, and particularly to a technique for automatically building a network configuration in which no conflicts occur, at the time of starting up the router device that is connected to the sub-networks.
(2) Description of the Related Art
With the expansion in the use and scale of communication networks, there exist a variety of transmission media, and there have been developed a variety of router devices (hereinafter also referred to simply as “router(s)”) for connecting sub-networks (to be also referred to simply as “subnet(s)”) that use homogeneous or heterogeneous transmission media. Note that homogeneous transmission media are used within the same subnet. In order to connect multiple subnets using a router, it is required that identifiers for uniquely identifying these subnets (hereinafter referred to as “Net ID(s)”) do to conflict with one another, i.e., values of Net IDs are required to be different. Note that “sub-network” is a smaller network unit that serves as one network system.
In order to meet this requirement, there is proposed a technique for verifying, at the time of starting up a router, that there is no conflict in the network configuration of a network system (hereinafter also referred to as “system”) comprised of multiple subnets that are connected (e.g. “Router and start up method thereof” disclosed in Japanese Patent No. 3373808).
In the above existing technique, a router verifies whether there is a flaw or not in the network configuration by broadcasting, to all subnets it is connected to, a message requesting their Net IDs, and by checking the received responses to such a request.
In this existing technique, it is possible to start up the router without any problems when there is no change in the network configuration of the system, such as in the case where a router is simply replaced with another one. However, when starting up a new router in order to integrate different systems with such a router, it is impossible to automatically solve the problem within the integrated system of conflicts on the networks.